Feed aggregator

arXiv:2403.04825v1 Announce Type: new Abstract: JWST observations are leading to important new insights into exoplanetary atmospheres through transmission spectroscopy. In order to harness the full potential of the broad spectral range and high sensitivity of JWST, atmospheric retrievals of exoplanets require a high level of robustness and accuracy in the underlying models. We present the VIRA retrieval framework which implements a range of modelling and inference capabilities motivated by early JWST observations of exoplanet transmission spectra. This includes three complementary approaches to modelling atmospheric composition, three atmospheric aerosol models, including a physically-motivated Mie scattering approach, and consideration of correlated noise. VIRA enables a cascading retrieval architecture involving a sequence of retrievals with increasing sophistication. We demonstrate VIRA using a JWST transmission spectrum of the hot Saturn WASP-39 b in the $\sim$1-5 $\mu$m range. In addition to confirming prior chemical inferences, we retrieve molecular abundances for H$_2$O, CO, CO$_2$, SO$_2$ and H$_2$S, resulting in super-solar elemental abundances of log(O/H)=$-2.0\pm0.2$, log(C/H)=$-2.1\pm0.2$ and log(S/H)=$-3.6\pm0.2$, along with C/O and S/O ratios of $0.83^{+0.05}_{-0.07}$ and $0.029^{+0.012}_{-0.009}$, respectively, in the free chemistry case. The abundances correspond to $20.1^{+10.5}_{-8.1}\times$, $28.2^{+16.3}_{-12.1}\times$ and $20.8^{+10.3}_{-7.5}\times$ solar values for O/H, C/H and S/H, respectively, compared to C/H $= 8.67\pm0.35 \times$ solar for Saturn. Our results demonstrate how JWST transmission spectroscopy combined with retrieval frameworks like VIRA can measure multi-elemental abundances for giant exoplanets and enable comparative characterisation with solar system planets.

A new convection scheme for exoplanet atmospheres

Convection is an essential process for transporting heat and moisture in planetary atmospheres. The standard Earth picture of moist convection rising from the surface is only one of a number of modes of convection. Notably, convection in atmospheres with a high condensible mass fraction (non-dilute atmospheres), or with a lighter background gas than the condensible species (e.g. water convection in a hydrogen dominated atmosphere) – acts very differently and can be much weaker or even shut down entirely in the latter case. Here I present a new mass-flux scheme which can capture these variations and simulate convection in a wide range of parameter space for use in 3D climate models. A validation using the case of Trappist-1 e is presented.

• Speaker: Edouard Barrier (University of Cambridge)
• Wednesday 13 March 2024, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.

Add to your calendar or Include in your list

A new convection scheme for exoplanet atmospheres

Convection is an essential process for transporting heat and moisture in planetary atmospheres. The standard Earth picture of moist convection rising from the surface is only one of a number of modes of convection. Notably, convection in atmospheres with a high condensible mass fraction (non-dilute atmospheres), or with a lighter background gas than the condensible species (e.g. water convection in a hydrogen dominated atmosphere) – acts very differently and can be much weaker or even shut down entirely in the latter case. Here I present a new mass-flux scheme which can capture these variations and simulate convection in a wide range of parameter space for use in 3D climate models. A validation using the case of Trappist-1 e is presented.

• Speaker: Edouard Barrier (University of Cambridge)
• Wednesday 13 March 2024, 13:15-13:40
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.

Add to your calendar or Include in your list

Effects of primordial black holes on early star formation

Primordial black holes (PBHs) have long been considered a promising candidate or an important component of dark matter (DM). Recent gravitational wave (GW) observations of binary black hole (BH) mergers have triggered renewed interest in PBHs in the stellar-mass (∼ 10 − 100 Msun) and supermassive regimes (∼ 107 − 1011 Msun). Although only a small fraction (≲ 1%) of dark matter in the form of PBHs is required to explain observations, these PBHs may play important roles in early structure/star formation. We use cosmological zoom-in simulations and semi-analytical models to explore the possible impact of stellar-mass PBHs on first star formation, taking into account two effects of PBHs: acceleration of structure formation and gas heating by BH accretion feedback. We find that the standard picture of first star formation is not changed by stellar-mass PBHs (allowed by existing observational constraints), and their global impact on the cosmic star formation history is likely minor. However, PBHs do alter the properties of the first star-forming halos and can potentially trigger the formation of direct-collapse BHs in atomic cooling halos. On the other hand, supermassive PBHs may play more important roles as seeds of massive structures that can explain the apparent overabundance of massive galaxies in recent JWST observations. Our tentative models and results call for future studies with improved modelling of the interactions between PBHs, particle DM, and baryons to better understand the effects of PBHs on early structure/star formation and their imprints in high-redshift observations.

• Speaker: Boyuan Liu (IoA)
• Friday 15 March 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

Constraining physics and astrophysics with multifrequency CMB data

The CMB anisotropies are measured in several microwave frequency bands. Having this frequency information allows us to separate signals that are due to different sources. We can easily make maps that are sensitive to specific frequency combinations, and in this way isolate the contribution from the primary CMB (early-Universe) and various other CMB interactions such as the Sunyaev—Zel’dovich (SZ) effect (the scattering of the CMB from electrons in the late Universe). I will talk about constraints on the SZ effect from Planck data using a new frequency-separation code, pyilc, which we use to isolate the signal while removing other late-Universe biases, in particular the infrared emission from star-forming galaxies. I will also show an application to beyond standard model interactions between the CMB and a non-trivial dark sector, and how we can use the CMB to constrain beyond-standard-model particle physics.

• Speaker: Fiona McCarthy (DAMTP)
• Wednesday 13 March 2024, 13:40-14:05
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.

Add to your calendar or Include in your list

Constraining physics and astrophysics with multifrequency CMB data

The CMB anisotropies are measured in several microwave frequency bands. Having this frequency information allows us to separate signals that are due to different sources. We can easily make maps that are sensitive to specific frequency combinations, and in this way isolate the contribution from the primary CMB (early-Universe) and various other CMB interactions such as the Sunyaev—Zel’dovich (SZ) effect (the scattering of the CMB from electrons in the late Universe). I will talk about constraints on the SZ effect from Planck data using a new frequency-separation code, pyilc, which we use to isolate the signal while removing other late-Universe biases, in particular the infrared emission from star-forming galaxies. I will also show an application to beyond standard model interactions between the CMB and a non-trivial dark sector, and how we can use the CMB to constrain beyond-standard-model particle physics.

• Speaker: Fiona McCarthy (DAMTP)
• Wednesday 13 March 2024, 13:40-14:05
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.

Add to your calendar or Include in your list

4 Min Read Peering Into the Tendrils of NGC 604 with NASA’s Webb Star-forming region NGC 604. Credits:
NASA, ESA, CSA, STScI

The formation of stars and the chaotic environments they inhabit is one of the most well-studied, but also mystery-shrouded, areas of cosmic investigation. The intricacies of these processes are now being unveiled like never before by NASA’s James Webb Space Telescope.

Two new images from Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) showcase star-forming region NGC 604, located in the Triangulum galaxy (M33), 2.73 million light-years away from Earth. In these images, cavernous bubbles and stretched-out filaments of gas etch a more detailed and complete tapestry of star birth than seen in the past.

Sheltered among NGC 604’s dusty envelopes of gas are more than 200 of the hottest, most massive kinds of stars, all in the early stages of their lives. These types of stars are B-types and O-types, the latter of which can be more than 100 times the mass of our own Sun. It’s quite rare to find this concentration of them in the nearby universe. In fact, there’s no similar region within our own Milky Way galaxy.

This concentration of massive stars, combined with its relatively close distance, means NGC 604 gives astronomers an opportunity to study these objects at a fascinating time early in their life.

Image: NIRCam View NGC 604 This image from NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) of star-forming region NGC 604 shows how stellar winds from bright, hot, young stars carve out cavities in surrounding gas and dust. NASA, ESA, CSA, STScI

In Webb’s near-infrared NIRCam image, the most noticeable features are tendrils and clumps of emission that appear bright red, extending out from areas that look like clearings, or large bubbles in the nebula. Stellar winds from the brightest and hottest young stars have carved out these cavities, while ultraviolet radiation ionizes the surrounding gas. This ionized hydrogen appears as a white and blue ghostly glow.

The bright orange-colored streaks in the Webb near-infrared image signify the presence of carbon-based molecules known as polycyclic aromatic hydrocarbons, or PAHs. This material plays an important role in the interstellar medium and the formation of stars and planets, but its origin is a mystery. As you travel farther from the immediate clearings of dust, the deeper red signifies molecular hydrogen. This cooler gas is a prime environment for star formation.

Webb’s exquisite resolution also provides insights into features that previously appeared unrelated to the main cloud. For example, in Webb’s image, there are two bright, young stars carving out holes in dust above the central nebula, connected through diffuse red gas. In visible-light imaging from NASA’s Hubble Space Telescope, these appeared as separate splotches.

Image: MIRI View NGC 604 This image from NASA’s James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) of star-forming region NGC 604 shows how large clouds of cooler gas and dust glow in mid-infrared wavelengths. This region is home to more than 200 of the hottest, most massive kinds of stars, all in the early stages of their lives. NASA, ESA, CSA, STScI

Webb’s view in mid-infrared wavelengths also illustrates a new perspective into the diverse and dynamic activity of this region. In the MIRI view of NGC 604, there are noticeably fewer stars. This is because hot stars emit much less light at these wavelengths, while the larger clouds of cooler gas and dust glow. Some of the stars seen in this image, belonging to the surrounding galaxy, are red supergiants – stars that are cool but very large, hundreds of times the diameter of our Sun. Additionally, some of the background galaxies that appeared in the NIRCam image also fade. In the MIRI image, the blue tendrils of material signify the presence of PAHs.

NGC 604 is estimated to be around 3.5 million years old. The cloud of glowing gases extends to some 1,300 light-years across.

Video: Explore the Images Explore Webb’s images of NGC 604 with Dr Jane Rigby (Webb Senior Project Scientist). Credit: NASA

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Downloads

Right click the images in this article to open a larger version in a new tab/window.
Download full resolution images for this article from the Space Telescope Science Institute.

Media Contacts

Laura Betz – laura.e.betz@nasa.gov, Rob Gutro – rob.gutro@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.

Related Information

Hubble’s view of NGC 604

Hubble’s view of NGC 604 host galaxy Triangulum (M33)

Star Lifecycle

More Webb News – https://science.nasa.gov/mission/webb/latestnews/

More Webb Images – https://science.nasa.gov/mission/webb/multimedia/images/

Webb Mission Page – https://science.nasa.gov/mission/webb/

Related For Kids

What is a galaxy?

What is a Nebula?

What is the Webb Telescope?

SpacePlace for Kids

En Español

Ciencia de la NASA

NASA en español 

Space Place para niños

Keep Exploring Related Topics James Webb Space Telescope

Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…

Stars

Stars Stories

Universe

Share

• 
  
  
• 
  
  
• 
  
  
• 
  
  

Details Last Updated Mar 09, 2024 Editor Stephen Sabia Contact Laura Betz laura.e.betz@nasa.gov Related Terms

• Astrophysics
• Galaxies, Stars, & Black Holes
• Goddard Space Flight Center
• James Webb Space Telescope (JWST)
• Missions
• Nebulae
• Science & Research
• Star-forming Nebulae
• The Universe

1 min read

Hubble Sees a Spiral Galaxy Edge-On This NASA/ESA Hubble Space Telescope image shows NGC 4423. ESA/Hubble & NASA, M. Sun

This NASA/ESA Hubble Space Telescope image shows NGC 4423, a galaxy that lies about 55 million light-years away in the constellation Virgo. In this image, NGC 4423 appears to have quite an irregular, tubular form, so it might be surprising to find out that it is in fact a spiral galaxy. Knowing this, we can make out the denser central bulge of the galaxy, and the less crowded surrounding disk (the part that comprises the spiral arms). 

If NGC 4423 were viewed face-on it would resemble the shape that we most associate with spiral galaxies: the spectacular curving arms sweeping out from a bright center, interspersed with dimmer, darker, less populated regions. But when observing the skies, we are constrained by the relative alignments between Earth and the objects that we are observing.

Text credit: European Space Agency (ESA)

Download this image

Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

Share

• 
  
  
• 
  
  
• 
  
  
• 
  
  

Details Last Updated Mar 08, 2024 Editor Andrea Gianopoulos Location Goddard Space Flight Center Related Terms

• Astrophysics
• Astrophysics Division
• Galaxies
• Goddard Space Flight Center
• Hubble Space Telescope
• Missions
• The Universe

Keep Exploring Discover More Topics From NASA Hubble Space Telescope

Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.

Galaxies Stories

Stars Stories

NASA Astrophysics

arXiv:2303.17676v2 Announce Type: replace Abstract: Very metal-poor stars ($\rm[Fe/H] $ 16) and obtain 38,000/41,000 additional metal-poor candidates with purity 29\%/52\%, respectively. We make our metal-poor star catalogs publicly available, for further exploration of the metal-poor Milky Way.

arXiv:2403.03974v1 Announce Type: new Abstract: We present new ALMA observations of CO, CN, CS, HCN and HCO$^{+}$ absorption seen against the bright and compact radio continuum sources of eight massive galaxies. Combined with archival observations, they reveal two distinct populations of molecular clouds, which we identify by combining CO emission and absorption profiles to unambiguously reveal each cloud's direction of motion and likely location. In galaxy disks, we see clouds with low velocity dispersions, low line of sight velocities and a lack of any systemic inflow or outflow. In galactic cores, we find high velocity dispersion clouds inflowing at up to 550 km/s. This provides observational evidence in favour of cold accretion onto galactic centres, which likely contributes to the fuelling of active galactic nuclei. We also see a wide range in the CO(2-1)/CO(1-0) ratios of the absorption lines. This is likely the combined effect of hierarchical substructure within the molecular clouds and continuum sources which vary in size with frequency.

By rotating a tank of water at 75 revolutions per minute, it’s possible to replicate some of the stunning, swirling patterns on Jupiter’s surface

All known natural phenomena fit into just a few categories and unifying them all is quantum field theory, says physicist Matt Strassler

Science, Volume 383, Issue 6687, Page 1038-1039, March 2024.

Exclusive: Significant discovery, made by James Webb telescope, provokes disagreement over conditions on planet’s surface

Astronomers have observed a distant planet that could be entirely covered in a deep water ocean, in findings that advance the search for habitable conditions beyond Earth.

The observations, by Nasa’s James Webb space telescope (JWST), revealed water vapour and chemical signatures of methane and carbon dioxide in the atmosphere of the exoplanet, which is twice Earth’s radius and about 70 light years away. This chemical mix is consistent with a water world where the ocean would span the entire surface, and a hydrogen-rich atmosphere, according to researchers from the University of Cambridge, although they do not envisage a balmy, inviting seascape.

Continue reading...

International Women's Day at the IoA

• 13.00 pm-14.00:Keynote Speaker: Ghina Halabi

• 14.00 pm-14.45:Flash Talks: Sandro Tacchella & Alejandra Castro

• 14.45 pm-15.15:Tea, Coffee and Cake

• 15.15 pm-16.30:An Interactive Session on Recognising Accomplishments

• 16.30 pm-16.50: Flash Talk: Greg Cooke

• 16.50 pm-17.00: Closing Remarks

• Speaker:
• Friday 08 March 2024, 13:00-17:00
• Venue: Hoyle Lecture Theatre, IoA .
• Series: Institute of Astronomy Extra Talks; organiser: iwd.

Add to your calendar or Include in your list

Eddington lecture 2024: The Dawn of Galaxy-scale Gravitational Wave Astronomy

For more than 15 years, NANO Grav and other pulsar-timing array collaborations have been carefully monitoring networks of pulsars across the Milky Way. The goal was to find a tell-tale correlation signature amid the data from all those pulsars that would signal the presence of an all-sky background of nanohertz-frequency gravitational waves, washing through the Galaxy. At the end of June 2023, the global pulsar-timing array community finally announced its evidence for this gravitational-wave background, along with a series of studies that interpreted this signal as either originating from a population of supermassive black-hole binary systems, or as relics from cosmological processes in the very early Universe. I will describe the journey up to this point (including the integral role that the IoA played), what led to the ultimate breakthrough, how this affects our knowledge of supermassive black holes and the early Universe, and what lies next for gravitational-wave astronomy at light-year wavelengths.

• Speaker: Dr Stephen Taylor, Vanderbilt University, Nashville, Tennessee, USA
• Thursday 07 March 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

Add to your calendar or Include in your list

Eddington lecture 2024: The Dawn of Galaxy-scale Gravitational Wave Astronomy

For more than 15 years, NANO Grav and other pulsar-timing array collaborations have been carefully monitoring networks of pulsars across the Milky Way. The goal was to find a tell-tale correlation signature amid the data from all those pulsars that would signal the presence of an all-sky background of nanohertz-frequency gravitational waves, washing through the Galaxy. At the end of June 2023, the global pulsar-timing array community finally announced its evidence for this gravitational-wave background, along with a series of studies that interpreted this signal as either originating from a population of supermassive black-hole binary systems, or as relics from cosmological processes in the very early Universe. I will describe the journey up to this point (including the integral role that the IoA played), what led to the ultimate breakthrough, how this affects our knowledge of supermassive black holes and the early Universe, and what lies next for gravitational-wave astronomy at light-year wavelengths.

• Speaker: Dr Stephen Taylor, Vanderbilt University, Nashville, Tennessee, USA
• Thursday 07 March 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

Add to your calendar or Include in your list

International Women's Day at the IoA

• 13.00 pm-14.00:Keynote Speaker: Ghina Halabi

• 14.00 pm-14.45:Flash Talks: Sandro Tacchella & Alejandra Castro

• 14.45 pm-15.15:Tea, Coffee and Cake

• 15.15 pm-16.30:An Interactive Session on Recognising Accomplishments

• 16.30 pm-16.50: Flash Talk: Greg Cooke

• 16.50 pm-17.00: Closing Remarks

• Speaker:
• Friday 08 March 2024, 13:00-17:00
• Venue: Hoyle Lecture Theatre, IoA .
• Series: Institute of Astronomy Extra Talks; organiser: .

Add to your calendar or Include in your list

Title to be confirmed

Abstract not available

• Speaker: Alvaro Ribas (IOA Cambridge)
• Tuesday 07 May 2024, 14:00-15:00
• Venue: MR14 DAMTP and online.
• Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.

Add to your calendar or Include in your list

Parity Violation in Cosmology

Parity symmetry is known to be violated in the weak interaction. Do the physical laws behind the unsolved problems of modern cosmology – cosmic inflation, dark matter, and dark energy – also violate parity symmetry? In this talk, we will discuss theoretical and observational possibilities of parity violation in cosmology, a topic that has received much attention in recent years.

• Speaker: Eiichiro Komatsu (MPA Garching)
• Monday 11 March 2024, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Inigo Zubeldia.

Add to your calendar or Include in your list