Webb Telescope observes a globular cluster sparkling with separate stars

On June 20, 2022, the James Webb Area Telescope spent simply over one hour watching Messier 92 (M92), a globular cluster 27,000 light-years away within the Milky Way halo. The statement—among the many very first science observations undertaken by Webb—is a part of Early Launch Science (ERS) program 1334, certainly one of 13 ERS applications designed to assist astronomers perceive methods to use Webb and profit from its scientific capabilities.

NASA spoke with Matteo Correnti from the Italian Area Company; Alessandro Savino from the College of California, Berkeley; Roger Cohen from Rutgers College; and Andy Dolphin from Raytheon Applied sciences to search out out extra about Webb’s observations of M92 and the way the group is utilizing the info to assist different astronomers. (Final November, Kristen McQuinn talked with NASA about her work on the dwarf galaxy WLM, which can also be a part of this program.)

Inform us about this ERS program. What are you making an attempt to perform?

Alessandro Savino: This specific program is targeted on resolved stellar populations. These are massive teams of stars like M92 which are very close by—shut sufficient that Webb can single out the person stars within the system. Scientifically, observations like these are very thrilling as a result of it’s from our cosmic neighborhood that we be taught a variety of the physics of stars and galaxies that we are able to translate to things that we see a lot farther away.

Matteo Correnti: We’re additionally making an attempt to know the telescope higher. This challenge has been instrumental for enhancing the calibration (ensuring the entire measurements are as correct as attainable), for enhancing the info for different astronomers and different comparable initiatives.

Why did you determine to take a look at M92 particularly?

Savino: Globular clusters like M92 are crucial for our understanding of stellar evolution. For many years they’ve been a main benchmark for understanding how stars work, how stars evolve. M92 is a traditional globular cluster. It is shut by; we perceive it comparatively nicely; it is certainly one of our references in research of stellar evolution and stellar methods.

Correnti: One more reason M92 is essential is as a result of it is without doubt one of the oldest globular clusters within the Milky Way, if not the oldest one. We predict M92 is between 12 and 13 billion years outdated. It incorporates a few of the oldest stars that we are able to discover, or at the least that we are able to resolve and characterize nicely. We are able to use close by clusters like this as tracers of the very historical universe.

Roger Cohen: We additionally selected M92 as a result of it is extremely dense: There are a variety of stars packed collectively very carefully. (The middle of the cluster is 1000’s of occasions denser than the area across the sun.) Taking a look at M92 permits us to check how Webb performs on this specific regime, the place we have to make measurements of stars which are very shut collectively.

What are the traits of a globular cluster that make it helpful for finding out how stars evolve?

Andy Dolphin: One of many major issues is that the majority of the celebs in M92 would have shaped at roughly the identical time and with roughly the identical mixture of parts, however with a variety of lots. So we are able to get a extremely good survey of this specific inhabitants of stars.

Savino: Additionally, because the stars all belong to the identical object (the identical globular cluster, M92), we all know they’re all about the identical distance away from us. That helps us so much as a result of we all know that variations in brightness between the completely different stars should be intrinsic, as an alternative of simply associated to how distant they’re. It makes the comparability with fashions a lot, a lot simpler.

This star cluster has already been studied with the Hubble Area Telescope and different telescopes. What can we see with Webb that we’ve not seen already?

Cohen: One of many essential variations between Webb and Hubble is that Webb operates at longer wavelengths, the place very cool, low-mass stars give off most of their mild. Webb is well-designed to look at very cool stars. We have been really in a position to attain all the way down to the bottom mass stars—stars lower than 0.1 occasions the mass of the sun. That is attention-grabbing as a result of that is very near the boundary the place stars cease being stars. (Beneath this boundary are brown dwarfs, that are so low-mass that they don’t seem to be in a position to ignite hydrogen of their cores.)

Correnti: Webb can also be so much sooner. To see the very faint low-mass stars with Hubble, you want a whole bunch of hours of telescope time. With Webb, it takes only a few hours.

Cohen: These observations weren’t really designed to push very onerous on the boundaries of the telescope. So it’s totally encouraging to see that we have been nonetheless in a position to detect such small, faint stars with out making an attempt actually, actually onerous.

What’s so attention-grabbing about these low-mass stars?

Savino: To begin with, they’re essentially the most quite a few stars within the universe. Second, from a theoretical viewpoint, they’re very attention-grabbing as a result of they’ve all the time been very troublesome to look at and characterize. Particularly stars lower than half the mass of the sun, the place our present understanding of stellar fashions is a bit more unsure.

Correnti: Finding out the sunshine these low-mass stars emit also can assist us higher constrain the age of the globular cluster. That helps us higher perceive when completely different elements of the Milky Way (just like the halo, the place M92 is situated) shaped. And that has implications for our understanding of cosmic historical past.

It appears to be like like there’s huge hole in the midst of the picture you captured. What’s that and why is it there?

Dolphin: This picture was made utilizing Webb’s Close to-Infrared Digicam (NIRCam). NIRCam has two modules, with a “chip hole” between the 2. The middle of the cluster is extraordinarily crowded, extraordinarily vivid. So that might have restricted the usefulness of the info from that area. The place of those pictures overlaps properly with Hubble knowledge accessible already.

Considered one of your major objectives was to supply instruments for different scientists. What are you significantly enthusiastic about?

Dolphin: One of many key sources we developed and have made accessible to the astronomical neighborhood is one thing referred to as the DOLPHOT NIRCam module. This works with an present piece of software program used to mechanically detect and measure the brightness of stars and different unresolved objects (issues with a star-like look). This was developed for cameras on Hubble. Including this module for NIRCam (in addition to one for NIRISS, one other of Webb’s devices) permits astronomers the identical evaluation process they know from Hubble, with the extra advantage of now having the ability to analyze Hubble and Webb knowledge in a single go to get combined-telescope star catalogs.

Savino: This can be a actually huge neighborhood service part. It is useful for everybody. It is making evaluation a lot simpler.