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Institute of Astronomy

 

Planet-eating stars hint at hidden chaos in the Milky Way

Astronomy News - Thu, 21/03/2024 - 10:25

Nature, Published online: 20 March 2024; doi:10.1038/d41586-024-00847-6

A handful of middle-aged stars seem to have gobbled up a planet, challenging assumptions about the stability of such systems.

Billions of stars have swallowed up a planet

Astronomy News - Thu, 21/03/2024 - 10:24

Twin stars that were born together should have the same composition, and the fact that many don’t suggests they have changed their chemistry by devouring planets

Documentation Software Engineer (Fixed Term)

Vacancies - Thu, 21/03/2024 - 00:00

Fixed-term: The funds for this post are available until 31 March 2026 in the first instance.

This is an exciting opportunity for Software Developer to join the Institute of Astronomy (IoA), University of Cambridge, as part of the data processing group for the European Space Agency's Gaia project (https://www.cosmos.esa.int/web/gaia), within the IoA Data Projects (CamCEAD) group. Gaia is a space observatory of the European Space Agency (ESA), launched in 2013, operational until 2025 and a final data release 2030/31. The core goal of the Gaia project is to produce the largest, most precise three-dimensional map of our galaxy by surveying over one billion stars and analysing their position, motion, and spectra, to reveal the Milky Way present-day structure and uncover its formation and evolution.

The successful candidate will work with the Gaia software development team and their main commitment will be the preparation of the documentation for the Gaia Data Releases (GDRs), with GDR4 foreseen not before end of 2025 and the final GDR5 by 2030/31. They will also be responsible for the enhancement and maintenance of the Gaia in the UK (https://www.gaia.ac.uk) webpage.

The successful candidate will hold a qualification (Master or equivalent) in a relevant discipline (e.g. computer science, mathematics, astronomy, physics or engineering). The Gaia consortium adopted LaTeX to write the documentation, hence its knowledge is essential. The documentation is also published as webpage, which makes the conversion from LaTeX to HTML one of the key responsibilities of the documentation team. In this context also the knowledge of XML and the understanding of web application, including accessibility, usability and security, are necessary. This skill will also be applicable for the Gaia in the UK webpage.

The Gaia documentation reflects the complexity of the project and many members of the consortium contribute to it, therefore the ability to handle complex documents is mandatory, as also the ability to proofread scientific or technical publications. Good team working and interpersonal skills will be required to communicate with the consortium development partners in other European institutes and ESA. Familiarity with astronomy and/or Gaia are desirable but not essential.

The role will grant opportunities to interact with the wider CamCEAD team, with the potential to contribute to other projects, including ground based astronomical surveys, medical imaging, and with the whole IoA community as well.

The ability to work as part of a team and have good communication skills is also required. The post-holder will be required to attend meetings both elsewhere in the UK and overseas.

Click the 'Apply' button below to register an account with our recruitment system (if you have not already) and apply online.

Closing Date: 23:59 GMT on Sunday, 21 April 2024

Applications will be reviewed after the closing date and short-listed candidates will be interviewed Friday, 3rd May 2024. Interviews will be held on-line.

Please indicate the contact details of three academic referees on the online application form and upload a full curriculum vitae (CV), list of publications, and a research/technical experience statement (with the research/technical experience statement totaling three pages max, in 11pt. font).

Note that references will only be requested for shortlisted candidates. The names and email contact details of three referees are a necessary part of the submission. If short-listed for interview, you should advise your nominated referees that their references will be requested with a deadline of Thursday, 2nd May 2024.

Please quote reference LG40991 on your application and in any correspondence about this vacancy.

The University actively supports equality, diversity and inclusion and encourages applications from all sections of society. The University of Cambridge thrives on the diversity of its staff and students. Applications from underrepresented groups are particularly welcome. We have an active Equality and Diversity Committee which continually works to further the aims of the Athena SWAN charter. The University has a number of family-friendly policies and initiatives, including a returning-carer scheme, childcare costs support, university workplace nurseries, university holiday play-schemes, and a shared parental-leave policy. As part of its commitment to providing a family-friendly environment for researchers, the IoA ensures that should parental leave be needed during the course of employment, there is provision for extension to contract to compensate for the parental leave taken.

The University has a responsibility to ensure that all employees are eligible to live and work in the UK.

The transient event in NGC 1566 from 2017 to 2019 I. An eccentric accretion disk and a turbulent, disk-dominated broad-line region unveiled by double-peaked Ca II and O I lines

Recent IoA Publications - Wed, 20/03/2024 - 10:46
arXiv:2402.12054v2 Announce Type: replace Abstract: NGC 1566 is known for exhibiting recurrent outbursts, which are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported to be accompanied by a change in Seyfert classification from Seyfert 1.8 to Seyfert 1.2. We analyze data from an optical spectroscopic variability campaign of NGC 1566 taken with the 9.2m SALT between July 2018 and October 2019 and supplement our data set with optical to near-infrared spectroscopic archival data taken by VLT/MUSE in September 2015 and October 2017. We observe the emergence and fading of a strong power-law-like blue continuum as well as strong variations in the Balmer, HeI, HeII lines and the coronal lines [FeVII], [FeX] and [FeXI]. Moreover, we detect broad double-peaked emission line profiles of OI 8446 and the CaII 8498,8542,8662 triplet. This is the first time that genuine double-peaked OI 8446 and CaII 8498,8542,8662 emission in AGN is reported in the literature. All broad lines show a clear redward asymmetry with respect to their central wavelength and we find indications for a significant blueward drift of the total line profiles during the transient event. We show that the double-peaked emission line profiles are well approximated by emission from a low-inclination, relativistic eccentric accretion disk, and that single-peaked profiles can be obtained by broadening due to scale-height dependent turbulence. Small-scale features in the OI and CaII lines suggest the presence of inhomogeneities in the broad-line region. We conclude that the broad-line region in NGC 1566 is dominated by the kinematics of a relativistic eccentric accretion disk. The broad-line region can be modeled to be vertically stratified with respect to scale-height turbulence. The observed blueward drift might be attributed to a low-optical-depth wind launched during the transient event.

High-precision astrometry with VVV -- II. A near-infrared extension of Gaia into the Galactic plane

Recent IoA Publications - Wed, 20/03/2024 - 10:23
arXiv:2403.12219v1 Announce Type: new Abstract: Aims. We use near-infrared, ground-based data from the VISTA Variables in the Via Lactea (VVV) survey to indirectly extend the astrometry provided by the Gaia catalog to objects in heavily-extincted regions towards the Galactic bulge and plane that are beyond Gaia's reach. Methods. We make use of the state-of-the-art techniques developed for high-precision astrometry and photometry with the Hubble Space Telescope to process the VVV data. We employ empirical, spatially-variable, effective point-spread functions and local transformations to mitigate the effects of systematic errors, like residual geometric distortion and image motion, and to improve measurements in crowded fields and for faint stars. We also anchor our astrometry to the absolute reference frame of the Gaia Data Release 3. Results. We measure between 20 and 60 times more sources than Gaia in the region surrounding the Galactic center, obtaining an single-exposure precision of about 12 mas and a proper-motion precision of better than 1 mas yr$^{-1}$ for bright, unsaturated sources. Our astrometry provides an extension of Gaia into the Galactic center. We publicly release the astro-photometric catalogs of the two VVV fields considered in this work, which contain a total of $\sim$ 3.5 million sources. Our catalogs cover $\sim$ 3 sq. degrees, about 0.5% of the entire VVV survey area.

NASA Radar Finds Ice Deposits at Moon’s North Pole

Astronomy News - Wed, 20/03/2024 - 10:05

4 min read

NASA Radar Finds Ice Deposits at Moon’s North Pole Additional evidence of water activity on moon

Using data from a NASA radar that flew aboard India’s Chandrayaan-1 spacecraft, scientists have detected ice deposits near the moon’s north pole. NASA’s Mini-SAR instrument, a lightweight, synthetic aperture radar, found more than 40 small craters with water ice. The craters range in size from 1 to 9 miles (2 to15 km) in diameter. Although the total amount of ice depends on its thickness in each crater, it’s estimated there could be at least 1.3 trillion pounds (600 million metric tons) of water ice.

Mini-SAR map of the Circular Polarization Ratio (CPR) of the north pole of the Moon. Fresh, “normal” craters (red circles) show high values of CPR inside and outside their rims. This is consistent with the distribution of rocks and ejected blocks around fresh impact features, indicating that the high CPR here is surface scattering. The “anomalous” craters (green circles) have high CPR within, but not outside their rims. Their interiors are also in permanent sun shadow. These relations are consistent with the high CPR in this case being caused by water ice, which is only stable in the polar dark cold traps. We estimate over 600 million cubic meters (1 cubic meter = 1 metric ton) of water in these features.

The Mini-SAR has imaged many of the permanently shadowed regions that exist at both poles of the Moons. These dark areas are extremely cold and it has been hypothesized that volatile material, including water ice, could be present in quantity here.  The main science object of the Mini-SAR experiment is to map and characterize any deposits that exist.   

Mini-SAR is a lightweight (less than 10 kg) imaging radar.  It uses the polarization properties of reflected radio waves to characterize surface properties.  Mini-SAR sends pulses of radar that are left-circular polarized.  Typical planetary surfaces reverse the polarization during the reflection of radio waves, so that normal echoes from Mini-SAR are right circular polarized.  The ratio of received power in the same sense transmitted (left circular) to the opposite sense (right circular) is called the circular polarization ratio (CPR).  Most of the Moon has low CPR, meaning that the reversal of polarization is the norm, but some targets have high CPR.  These include very rough, fresh surfaces (such as a young, fresh crater) and ice, which is transparent to radio energy and multiply scatters the pulses, leading to an enhancement in same sense reflections and hence, high CPR.  CPR is not uniquely diagnostic of either roughness or ice; the science team must take into account the environment of the occurrences of high CPR signal to interpret its cause.

The fresh impact crater Main L (14 km diameter, 81.4° N, 22° E ), which shows high CPR inside and outside its rim. SC is the “same sense, circular” polarization; CPR is “circular polarization ratio.” The histograms at right show that the high CPR values within (red line) and outside the crater rim (green line) are nearly identical.

Numerous craters near the poles of the Moon have interiors that are in permanent sun shadow.  These areas are very cold and water ice is stable there essentially indefinitely.  Fresh craters show high degrees of surface roughness (high CPR) both inside and outside the crater rim, caused by sharp rocks and block fields that are distributed over the entire crater area.  However, Mini-SAR has found craters near the north pole that have high CPR inside, but not outside their rims.  This relation suggests that the high CPR is not caused by roughness, but by some material that is restricted within the interiors of these craters.  We interpret this relation as consistent with water ice present in these craters.  The ice must be relatively pure and at least a couple of meters thick to give this signature.

An “anomalous” crater on the floor of Rozhdestvensky (9 km Diameter, 84.3° N, 157° W), near the north pole of the Moon. This feature shows high CPR within the crater rim, but low CPR outside, suggesting that roughness (which occurs throughout a fresh crater) is not the cause of the elevated CPR. This feature’s interior is in permanent sun shadow. SC stands for “same sense, circular”, OC stands for “opposite sense, circular” and CPR is the “circular polarization ratio.” The histogram of CPR values clearly shows that interior points (red line) have higher CPR values than those outside the crater rim (green line).

The estimated amount of water ice potentially present is comparable to the quantity estimated solely from the previous mission of Lunar Prospector’s neutron data (several hundred million metric tons.)  The variation in the estimates between Mini-SAR and the Lunar Prospector’s  neutron spectrometer is due to the fact that it only measures to depths of about one-half meter, so it would underestimate the total quantity of water ice present.  At least some of the polar ice is mixed with lunar soil and thus, invisible to our radar.

“The emerging picture from the multiple measurements and resulting data of the instruments on lunar missions indicates that water creation, migration, deposition and retention are occurring on the moon,” said Paul Spudis, principal investigator of the Mini-SAR experiment at the Lunar and Planetary Institute in Houston. “The new discoveries show the moon is an even more interesting and attractive scientific, exploration and operational destination than people had previously thought.”

“After analyzing the data, our science team determined a strong indication of water ice, a finding which will give future missions a new target to further explore and exploit,” said Jason Crusan, program executive for the Mini-RF Program for NASA’s Space Operations Mission Directorate in Washington.

The Mini-SAR’s findings are being published in the journal Geophysical Research Letters. The results are consistent with recent findings of other NASA instruments and add to the growing scientific understanding of the multiple forms of water found on the moon. The agency’s Moon Mineralogy Mapper discovered water molecules in the moon’s polar regions, while water vapor was detected by NASA’s Lunar Crater Observation and Sensing Satellite, or LCROSS.

Mini-SAR and Moon Mineralogy Mapper are two of 11 instruments on the Indian Space Research Organization’s Chandrayaan-1. The Applied Physics Laboratory in Laurel, Md., performed the final integration and testing on Mini-SAR. It was developed and built by the Naval Air Warfare Center in China Lake, Calif., and several other commercial and government contributors.

Get more information about Chandrayaan-1

March 2, 2010

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The S-PLUS Fornax Project (S+FP): A first 12-band glimpse of the Fornax galaxy cluster

Recent IoA Publications - Tue, 19/03/2024 - 10:09
arXiv:2403.10697v1 Announce Type: new Abstract: The Fornax galaxy cluster is the richest nearby (D ~ 20 Mpc) galaxy association in the southern sky. As such, it provides a wealth of oportunities to elucidate on the processes where environment holds a key role in transforming galaxies. Although it has been the focus of many studies, Fornax has never been explored with contiguous homogeneous wide-field imaging in 12 photometric narrow- and broad-bands like those provided by the Southern Photometric Local Universe Survey (S-PLUS). In this paper we present the S-PLUS Fornax Project (S+FP) that aims to comprehensively analyse the galaxy content of the Fornax cluster using S-PLUS. Our data set consists of 106 S-PLUS wide-field frames (FoV ~ 1.4 x 1.4 deg$^2$) observed in five SDSS-like ugriz broad-bands and seven narrow-bands covering specific spectroscopic features like [OII], CaII H+K, H$\delta$, G-band, Mg b triplet, H$\alpha$, and the CaII triplet. Based on S-PLUS specific automated photometry, aimed at correctly detecting Fornax galaxies and globular clusters in S-PLUS images, our dataset provides the community with catalogues containing homogeneous 12-band photometry for ~ 3 x 10$^6$ resolved and unresolved objects within a region extending over ~ 208 deg$^2$ (~ 5 Rvir in RA) around Fornax' central galaxy, NGC 1399. We further explore the EAGLE and IllustrisTNG cosmological simulations to identify 45 Fornax-like clusters and generate mock images on all 12 S-PLUS bands of these structures down to galaxies with M$\star \geq 10^8$ M$\odot$. The S+FP dataset we put forward in this first paper of a series will enable a variety of studies some of which are briefly presented.

NASA’s Swift Temporarily Suspends Science Operations

Astronomy News - Tue, 19/03/2024 - 09:47

1 min read

NASA’s Swift Temporarily Suspends Science Operations Swift, illustrated here, is a collaboration between NASA’s Goddard Space Flight Center in Greenbelt, Maryland, Penn State in University Park, the Los Alamos National Laboratory in New Mexico, and Northrop Grumman Innovation Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory in Italy, and the Italian Space Agency.NASA’s Goddard Space Flight Center

On March 15, NASA’s Neil Gehrels Swift Observatory entered into safe mode, temporarily suspending science operations due to degrading performance from one of its three gyroscopes (gyros), which are used to point the observatory for making observations. The rest of the spacecraft remains in good health.

Swift is designed to successfully operate without one of its gyros if necessary; however, a software update is required. The team is working on the flight software update that would permit the spacecraft to continue science operations using its two remaining gyros. The team is working to return Swift to science observations as soon as possible.

Launched in 2004, Swift has been observing the high-energy universe for nearly 20 years. Stay tuned to nasa.gov/swift for more updates.

Share Details Last Updated Mar 18, 2024 EditorJamie Adkins Related Terms

Titan’s sand dunes may be made of smashed up small moons

Astronomy News - Tue, 19/03/2024 - 09:46

The sand dunes that splay across the surface of Saturn’s moon Titan may be made of the ground-up remains of ancient irregular moons, rather than atmospheric particles

Mon 20 May 13:00: Title to be confirmed

Next External Talks - Mon, 18/03/2024 - 17:42
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Detection of ionized hydrogen and oxygen from a very luminous and young galaxy 13.4 billion years ago

Recent IoA Publications - Mon, 18/03/2024 - 12:15
arXiv:2403.10491v1 Announce Type: new Abstract: The James Webb Space Telescope (JWST) has discovered a surprising population of bright galaxies in the very early universe (10 using the JWST Mid-Infrared Instrument, MIRI. These detections place the bright galaxy GHZ2/GLASS-z12 at z=12.33+/-0.02, making it the most distant astronomical object with direct spectroscopic detection of these lines and the brightest confirmed object at this epoch. These observations provide key insights into the conditions of this primeval galaxy, which shows hard ionizing conditions rarely seen in the local Universe and likely driven by compact, young (

Modeling JWST MIRI-MRS Observations of T Cha: Mid-IR Noble Gas Emission Tracing a Dense Disk Wind

Recent IoA Publications - Mon, 18/03/2024 - 11:44
arXiv:2403.09780v1 Announce Type: new Abstract: [Ne II] 12.81 $\mu\mathrm{m}$ emission is a well-used tracer of protoplanetary disk winds due to its blueshifted line profile. MIRI-MRS recently observed T Cha, detecting this line along with lines of [Ne III], [Ar II] and [Ar III], with the [Ne II] and [Ne III] lines found to be extended while the [Ar II] was not. In this complementary work, we use these lines to address long-debated questions about protoplanetary disk winds regarding their mass-loss rate, the origin of their ionization, and the role of magnetically-driven winds as opposed to photoevaporation. To this end, we perform photoionization radiative transfer on simple hydrodynamic wind models to map the line emission. We compare the integrated model luminosities to those observed with MIRI-MRS to identify which models most closely reproduce the data and produce synthetic images from these to understand what information is captured by measurements of the line extents. Along with the low degree of ionization implied by the line ratios, the relative compactness of [Ar II] compared to [Ne II] is particularly constraining. This requires Ne II production by hard X-rays and Ar II production by soft X-rays (and/or EUV) in an extended ($\gtrsim 10$ au) wind that is shielded from soft X-rays - necessitating a dense wind with material launched on scales down to ~1 au. Such conditions could be produced by photoevaporation, whereas an extended MHD wind producing equal shielding would likely underpredict the line fluxes. However, a tenuous inner MHD wind may still contribute to shielding the extended wind. This picture is consistent with constraints from spectrally-resolved line profiles.

Tue 19 Mar 14:00: Primordial black holes in the dark matter halo of our Galaxy

IoA Institute of Astronomy Talk Lists - Mon, 18/03/2024 - 11:09
Primordial black holes in the dark matter halo of our Galaxy

If there are primordial black holes in the dark matter halo, they must collide with the Galactic neutron stars (NSs) and produce light black holes (LBHs), with masses below 1.4 M_Sun. This has observational consequences that may be checked by microlensing, by LIGO -Virgo-Kagra interferometers detecting gravitational waves from collisions of LBHs with NSs and BHs, and (possibly) by detecting LBHs in X-ray binaries and from pulsars statistics.

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Tue 19 Mar 14:00: Primordial black holes in the dark matter halo of our Galaxy

Next Wednesday Seminars - Mon, 18/03/2024 - 11:09
Primordial black holes in the dark matter halo of our Galaxy

If there are primordial black holes in the dark matter halo, they must collide with the Galactic neutron stars (NSs) and produce light black holes (LBHs), with masses below 1.4 M_Sun. This has observational consequences that may be checked by microlensing, by LIGO -Virgo-Kagra interferometers detecting gravitational waves from collisions of LBHs with NSs and BHs, and (possibly) by detecting LBHs in X-ray binaries and from pulsars statistics.

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Did ‘alien’ debris hit Earth? Startling claim sparks row at scientific meeting

Astronomy News - Sat, 16/03/2024 - 15:14

Nature, Published online: 13 March 2024; doi:10.1038/d41586-024-00774-6

Astrophysicist Avi Loeb says that an interstellar meteor showered Earth with particles. At a planetary science conference this week, researchers begged to differ.

Do black holes explode? The 50-year-old puzzle that challenges quantum physics

Astronomy News - Sat, 16/03/2024 - 15:13

Nature, Published online: 14 March 2024; doi:10.1038/d41586-024-00768-4

Stephen Hawking’s paradoxical finding that black holes don’t live forever has profound, unresolved implications for the quest for unifying theories of reality.