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Japan's SLIM moon lander regains power nine days after botched landing

Astronomy News - Tue, 30/01/2024 - 10:43

SLIM was put into hibernation after landing on the moon upside down, but it woke up when sunlight hit its solar panels

JWST has taken extraordinary images of 19 nearby spiral galaxies

Astronomy News - Tue, 30/01/2024 - 10:43

Astronomers have used the James Webb Space Telescope to take astonishingly detailed images of spiral galaxies, revealing how and where they spark star formation

The Ingenuity helicopter’s Mars mission is over, but it left a legacy

Astronomy News - Tue, 30/01/2024 - 10:43

After nearly three years of exploring Mars, NASA’s Ingenuity helicopter has taken its final flight – but its astounding performance is a good sign for future drones on other worlds

Galaxy smash-ups may explain strange light from early universe

Astronomy News - Tue, 30/01/2024 - 10:43

Light from hydrogen in the early universe has baffled astronomers, but researchers have spotted interacting galaxies that could explain how it makes its way to us

A dynamical measure of the black hole mass in a quasar 11 billion years ago. (arXiv:2401.14567v1 [astro-ph.GA])

Recent IoA Publications - Mon, 29/01/2024 - 10:43

Tight relationships exist in the local universe between the central stellar properties of galaxies and the mass of their supermassive black hole. These suggest galaxies and black holes co-evolve, with the main regulation mechanism being energetic feedback from accretion onto the black hole during its quasar phase. A crucial question is how the relationship between black holes and galaxies evolves with time; a key epoch to probe this relationship is at the peaks of star formation and black hole growth 8-12 billion years ago (redshifts 1-3). Here we report a dynamical measurement of the mass of the black hole in a luminous quasar at a redshift of 2, with a look back time of 11 billion years, by spatially resolving the broad line region. We detect a 40 micro-arcsecond (0.31 pc) spatial offset between the red and blue photocenters of the H$\alpha$ line that traces the velocity gradient of a rotating broad line region. The flux and differential phase spectra are well reproduced by a thick, moderately inclined disk of gas clouds within the sphere of influence of a central black hole with a mass of 3.2x10$^{8}$ solar masses. Molecular gas data reveal a dynamical mass for the host galaxy of 6x10$^{11}$ solar masses, which indicates an under-massive black hole accreting at a super-Eddington rate. This suggests a host galaxy that grew faster than the supermassive black hole, indicating a delay between galaxy and black hole formation for some systems.

On the incidence of episodic accretion in Class I YSOs from VVV. (arXiv:2401.14472v1 [astro-ph.SR])

Recent IoA Publications - Mon, 29/01/2024 - 10:41

Episodic accretion is one of the competing models to explain the observed luminosity spread in young stellar clusters. These short-lived high accretion events could also have a strong impact on planet formation. Observations of high-amplitude variability in young stellar objects (YSOs) due to large changes in the accretion rate provide direct observational evidence for episodic accretion. However, there are still uncertainties in the frequency of these events and if episodic accretion is universal among YSOs. To determine the frequency of outbursts in Class I YSOs, we built a large and robust sample of objects at this evolutionary stage, and searched for high-amplitude near-infrared ($\Delta K_{\rm S}>2$~mag) variability in the VIRAC2 database of the Vista Variables in the Via Lactea (VVV) survey. By complementing with near-IR (2MASS and DENIS) and mid-IR (WISE/Neo-WISE) data, we find that from $\sim$ 7000 Class I YSOs, 97 objects can be classified as eruptive variable YSOs. The duration of the outbursts vary from a few months to longer than 9 years, and cover a similar range of amplitudes. Values of $\Delta K_{\rm S}>5$~mag, however, are only observed in outbursts with duration longer than 9 years. When considering different effects of completeness and contamination we estimate that the incidence of episodic accretion in Class I YSOs is between 2\% and 3\%. Finally, we determine a recurrence timescale of long-term outbursts (a.k.a FUors) of $\tau=1.75^{+1.12}_{-0.87}$~kyr. The latter value agrees with previous estimates and is in line with the expectations of higher frequency of FUor outbursts during younger stages of evolution.

The most variable VVV sources: eruptive protostars, dipping giants in the Nuclear Disc and others. (arXiv:2401.14471v1 [astro-ph.SR])

Recent IoA Publications - Mon, 29/01/2024 - 10:41

We have performed a comprehensive search of a VISTA Variables in the Via Lactea (VVV) database of 9.5 yr light curves for variable sources with $\Delta K_s \ge 4$ mag, aiming to provide a large sample of high amplitude eruptive young stellar objects (YSOs) and detect unusual or new types of infrared variable source. We find 222 variable or transient sources in the Galactic bulge and disc, most of which are new discoveries. The sample mainly comprises novae, YSOs, microlensing events, Long Period Variable stars (LPVs) and a few rare or unclassified sources. Additionally, we report the discovery of a significant population of aperiodic late-type giant stars suffering deep extinction events, strongly clustered in the Nuclear Disc of the Milky Way. We suggest that these are metal-rich stars in which radiatively driven mass loss has been enhanced by super-solar metallicity. Among the YSOs, 32/40 appear to be undergoing episodic accretion. Long-lasting YSO eruptions have a typical rise time of $\sim$2 yr, somewhat slower than the 6-12 month timescale seen in the few historical events observed on the rise. The outburst durations are usually at least 5 yr, somewhat longer than many lower amplitude VVV events detected previously. The light curves are diverse in nature, suggesting that multiple types of disc instability may occur. Eight long-duration extinction events are seen wherein the YSO dims for a year or more, attributable to inner disc structure. One binary YSO in NGC 6530 displays periodic extinction events (P=59 days) similar to KH 15D.

Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO. (arXiv:2401.14470v1 [astro-ph.SR])

Recent IoA Publications - Mon, 29/01/2024 - 10:41

During the pre-main-sequence evolution, Young Stellar Objects (YSOs) assemble most of their mass during the episodic accretion process. The rarely seen FUOr-type events (FUOrs) are valuable laboratories to investigate the outbursting nature of YSOs. Here, we present multi-wavelength detection of a high-amplitude eruptive source in the young open cluster VdBH 221 with an ongoing outburst, including optical to mid-infrared time series and near-infrared spectra. The initial outburst has an exceptional amplitude of $>$6.3 mag in Gaia and 4.6 mag in $K_s$, with a peak luminosity up to 16 $L_{\odot}$ and a peak mass accretion rate of 1.4 $\times$ 10$^{-5}$ $M_\odot$ yr$^{-1}$. The optical to infrared spectral energy distribution (SED) of this object is consistent with a low-mass star (0.2$M_\odot$) with a modest extinction ($A_V < 2$ mag). A 100-d delay between optical and infrared rising stages is detected, suggesting an outside-in origin of the instability. The spectroscopic features of this object reveal a self-luminous accretion disc, very similar to FU Orionis, with a low line-of-sight extinction. Most recently, there has been a gradual increase in brightness throughout the wavelength range, possibly suggesting an enhancement of the mass accretion rate.

Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey. (arXiv:2401.14464v1 [astro-ph.SR])

Recent IoA Publications - Mon, 29/01/2024 - 10:40

During the pre-main-sequence (pre-MS) evolution stage of a star, significant amounts of stellar mass are accreted during episodic accretion events, such as multi-decade FUor-type outbursts. Here, we present a near-infrared spectroscopic follow-up study of 33 high-amplitude (most with $\Delta K_s$ > 4 mag) variable sources discovered by the Vista Variables in the Via Lactea (VVV) survey. Based on the spectral features, 25 sources are classified as eruptive young stellar objects (YSOs), including 15 newly identified FUors, six with long-lasting but EXor-like bursts of magnetospheric accretion and four displaying outflow-dominated spectra. By examining the photometric behaviours of eruptive YSOs, we found most FUor-type outbursts have higher amplitudes ($\Delta K_s$ and $\Delta W2$), faster eruptive timescales and bluer infrared colours than the other outburst types. In addition, we identified seven post-main sequence variables apparently associated with deep dipping events and an eruptive star with deep AlO absorption bands resembling those seen in the V838 Mon stellar merger.

Japan: Moon lander Slim comes back to life and resumes mission

Astronomy News - Mon, 29/01/2024 - 10:26

The lander has begun sending photos, including that of a nearby rock nicknamed "toy poodle".

Fri 17 May 11:30: Title to be confirmed

IoA Institute of Astronomy Talk Lists - Mon, 29/01/2024 - 09:56

Title to be confirmed

Abstract not available

Speaker: Harry Bevins (KICC)
Friday 17 May 2024, 11:30-12:30
Venue: Ryle seminar room + online.
Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

Add to your calendar or Include in your list

Weakening of magnetic braking in cataclysmic variables explains the dearth of period bouncers. (arXiv:2401.14389v1 [astro-ph.SR])

Recent IoA Publications - Sat, 27/01/2024 - 15:38

Period bouncers are cataclysmic variables (CVs) that have evolved past their orbital period minimum. The strong disagreement between theory and observations of the relative fraction of period bouncers is a severe shortcoming in the understanding of CV evolution. We test the implications of the hypothesis that magnetic braking (MB), which is suggested to be an additional angular momentum loss (AML) mechanism for CVs below the period gap ($P_\mathrm{orb}\lesssim 120$ min), weakens around their period minimum. We compute the evolution of CV donors below the period gap using the MESA code, assuming that the evolution of the system is driven by AML by gravitational wave radiation (GWR) and MB. We parametrize the MB strength as $\mathrm{AML_{MB}}=\kappa\mathrm{AML_{GWR}}$. We compute two qualitatively different sets of models, one where $\kappa$ is a constant and the other where $\kappa$ depends on stellar parameters. We find that in the latter set of models, $\kappa$ decreases as the CV approaches the period minimum ($P_\mathrm{orb}\approx80\,$ min), beyond which $\kappa\approx0$. This stalls their evolution so that they spend a long time in the observed period minimum spike ($80\lesssim P_\mathrm{orb}/\,\mathrm{min}\lesssim 86$). Here they become difficult to distinguish from pre-bounce systems in the spike. A strong decrease in mass-transfer rate makes them virtually undetectable as they evolve further. We also discuss the physical processes, such as dynamo action, white dwarf magnetism and dead zones, that may cause such a weakening of MB at short orbital periods. The weakening magnetic braking formalism solves the problem of the lack of period bouncers in CV observational surveys.

Circumbinary discs for stellar population models. (arXiv:2401.14315v1 [astro-ph.SR])

Recent IoA Publications - Sat, 27/01/2024 - 15:37

We develop a rapid algorithm for the evolution of stable, circular, circumbinary discs suitable for parameter estimation and population synthesis modelling. Our model includes disc mass and angular momentum changes, accretion on to the binary stars, and binary orbital eccentricity pumping. We fit our model to the post-asymptotic giant branch (post-AGB) circumbinary disc around IRAS 08544-4431, finding reasonable agreement despite the simplicity of our model. Our best-fitting disc has a mass of about $0.01\, \mathrm{M}_{\odot }$ and angular momentum $2.7\times 10^{52}\, \mathrm{g}\, \mathrm{cm}^{2}\, \mathrm{s}^{-1}\simeq 9 \,\mathrm{M}_{\odot }\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{au}$, corresponding to 0.0079 and 0.16 of the common-envelope mass and angular momentum, respectively. The best-fitting disc viscosity is $\alpha _\mathrm{disc} = 5 \times 10^{-3}$ and our tidal torque algorithm can be constrained such that the inner edge of the disc $R_{\mathrm{in}}\sim 2a$. The inner binary eccentricity reaches about 0.13 in our best-fitting model of IRAS 08544-4431, short of the observed 0.22. The circumbinary disc evaporates quickly when the post-AGB star reaches a temperature of $\sim \! 6\times 10^4\, \mathrm{K}$, suggesting that planetismals must form in the disc in about $10^{4}\, \mathrm{yr}$ if secondary planet formation is to occur, while accretion from the disc on to the stars at about 10 times the inner-edge viscous rate can double the disc lifetime.

NASA’s LRO Spots Japan’s Moon Lander

Astronomy News - Sat, 27/01/2024 - 15:15

1 min read

Preparations for Next Moonwalk Simulations Underway (and Underwater)

On Jan. 19, 2024, at 10:20 a.m. EST, the JAXA (Japan Aerospace Exploration Agency) Smart Lander for Investigating Moon (SLIM) landed on the lunar surface. Five days later, NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft passed over the landing site and photographed SLIM.

NASA’s Lunar Reconnaissance Orbiter captured this image of the JAXA (Japan Aerospace Exploration Agency) SLIM lander on the Moon’s surface on Jan. 24, 2024. SLIM landed at 13.3160 degrees south latitude, 25.2510 degrees east longitude, at an elevation of minus 2,992 feet (minus 912 meters). The image is 2,887 feet wide (880 meters), and lunar north is up. (LROC NAC frame M14607392143L)NASA/Goddard/Arizona State University

LRO acquired the image at an altitude of about 50 miles (80 km). Bright streaks on the left side of the image are rocky material ejected from the nearby, relatively young Shioli crater.

Japan is the fifth nation to complete a soft landing on the lunar surface.

This image pair shows LRO views of the area surrounding the SLIM site before (frame M1254087075L) and after (frame M1460739214L) its landing. Note the slight change in reflectance around the lander due to engine exhaust sweeping the surface. These images are enlarged by a factor of two, and are about 1,444 feet (440 meters) wide.NASA/Goddard/Arizona State University A composite image dividing the before image from after. Features that are the same in both images disappear, highlighting the changes in surface brightness from the rocket plume. The image is 2,887 feet wide (880 meters), and lunar north is up.NASA/Goddard/Arizona State University

LRO is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for the agency’s Science Mission Directorate at NASA Headquarters in Washington. Launched on June 18, 2009, LRO has collected a treasure trove of data with its seven powerful instruments, making an invaluable contribution to our knowledge about the Moon. Arizona State University manages and operates the Lunar Reconnaissance Orbiter Camera, LROC.

More on this story from Arizona State University's LRO Camera website

Media Contact:
Nancy N. Jones
NASA’s Goddard Space Flight Center, Greenbelt, Md.

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Details Last Updated Jan 26, 2024 EditorMadison ArnoldContactNancy N. Jonesnancy.n.jones@nasa.govLocationGoddard Space Flight Center Related Terms