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Rare green comet C/2022 E3 is about to make its closest pass by Earth

Astronomy News - 26 January 2023 - 9:42am

A comet that last passed by Earth about 50,000 years ago is coming around again and will make its closest pass on 1 February, at which point it may be visible with the naked eye

Webb telescope hunts life's icy chemical origins

Astronomy News - 25 January 2023 - 9:47am

The new super space telescope has been studying some of the darkest, coldest regions of space.

Applied technology will block light from multi-star systems to search for Earth-like planets

Astronomy News - 25 January 2023 - 9:46am
PROJECT

Multi-star Wavefront Control (MSWC)

SNAPSHOT

Multi-star wavefront control technology enables imaging planets in systems with multiple suns (such as Alpha Centauri, the nearest star system to us) and searching them for signs of life.

In 1990, at the behest of Carl Sagan, the Voyager mission took a photo of Earth from 3.7 billion miles away (image at left). The next challenge is to take a similar image of an Earth-like planet orbiting another star. MSWC technology could enable images of multi-star systems such as Alpha Centauri (simulated image on the right; image credit: J. Males, University of Arizona), the nearest star system to the Sun that could potentially host such planets.

For millennia, people have wondered if life exists elsewhere in the universe. To answer this question, we need to directly image exoplanets (planets orbiting stars other than the Sun) and search them for signs of life. Many nearby stars, however, reside in multi-star systems (i.e., systems with more than one star). In fact, Sun-like stars are more likely to be in multi-star systems—such as Alpha Centauri, the nearest star system to the Sun—than be single stars like our Sun. Therefore, to detect life we will likely need to image exoplanets in these multi-star systems. A newly developed technology, Multi-Star Wavefront Control (MSWC), provides just this kind of capability.

Planets are much dimmer than stars and typically light from nearby stars must be suppressed to image them. Broadly speaking, instruments that suppress starlight inside the telescope are called coronagraphs and those that do it externally are called starshades.

NASA’s next flagship telescope will be the Nancy Grace Roman Space Telescope, scheduled to launch by May 2027, and will include a technology demonstration of a coronagraphic instrument capable of imaging large planets near their host stars. NASA is also embarking on the development of the next flagship after Roman, provisionally named the “Habitable Worlds Observatory.” Recommended by the 2020 Decadal Survey in Astronomy and Astrophysics, this flagship will address the guidance to identify at least 25 Earth-like planets and characterize them for evidence of life. In addition, NASA may select smaller missions that support the objective of discovering and characterizing habitable planets.

Although binary stars are scientifically a very attractive class of targets for such missions (especially Alpha Centauri), they present a technical challenge because light from both stars needs to be suppressed to image any nearby planets. Using a combination of a coronagraph and/or starshade to suppress light from each star is not optimal because of the added cost and risk. In addition, current coronagraphic systems can suppress starlight around an individual star, but cannot suppress the cross-contamination of starlight between stars. Eliminating this cross-contamination is the key challenge that must be overcome to image planets around binary star systems.

Multi-Star Wavefront Control (MSWC) was developed to address this challenge. Invented at NASA Ames in 2014, it relies on two innovations that work together. The first is a way to control a deformable mirror (DM) to suppress light from two stars independently. This is done by using two different sets of shapes (spatial frequency modes) on the DM for different stars. The second technique, called “super-Nyquist wavefront control,” is a way to enable deformable mirrors to suppress starlight beyond their normal limits by using a special "mild grating,” shown as a grid of blue dots in the image below. Normally, a DM can only suppress starlight in a small region around a star, like a single tent pole (the star) supporting a small tent (DM control region). This poses a problem when imaging binary stars, because a typical DM can only suppress starlight from both stars if those stars’ two regions overlap. However, binary stars tend to be far apart, so there is no overlap, like two small tents that are far away from each other. The mild grating solves this problem by creating a grid of faint copies of the second star (so-called “diffraction orders”), extending the reach of the DM to a much larger region around each star, similar to how a grid of tent poles can support a larger tent than a single pole. Using these two techniques, a coronagraph can overcome cross-contamination and increase the starlight contrast to image exoplanets in binary star systems.

Left: Microscope image of an optical mask that enables suppression of stars in multi-star systems to reveal planets in such systems. Middle and right: the enabling element is a grid of dots (mild grating), shown in this design image at different zoom levels.

Because deformable mirrors will be present in essentially all future coronagraphic mission concepts, MSWC is compatible with most of them, without requiring a major instrument redesign. This compatibility enabled MSWC to be accepted as a contributed mode on the Roman Space Telescope’s Coronagraph Instrument, with only slight modifications of the single-star instrument masks. Testing MSWC on the sky with Roman’s coronagraph will demonstrate this important technology to enable imaging of exoplanets in binary star systems, and has the potential to detect planets around binaries like Alpha Centauri.

The MSWC team has been steadily maturing the technology through simulations as well as demonstrations at the Ames Coronagraph Experiment Laboratory and on the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument on the Subaru Telescope—a ground-based telescope operated by the National Astronomical Observatory of Japan. Also, over the past few years, the team extended MSWC testing to the High Contrast Imaging Testbed (HCIT) at NASA’s Jet Propulsion Laboratory (JPL), a state-of-the-art facility for high-contrast demonstrations in vacuum.

Team members working at the High Contrast Imaging Testbed (HCIT) facility at NASA’s JPL. Pictured left to right: Eduardo Bendek, Ruslan Belikov, Dan Sirbu, and David Marx. The goal of these tests is to perform a vacuum demonstration of the MSWC technology by suppressing the glare of more than one star to reveal dim planets that are otherwise hidden.

MSWC has made significant strides, demonstrating the basic feasibility of suppressing starlight from more than one star, as well as doing so for stars that are separated beyond the conventional limits of deformable mirrors. Now, the team is hard at work to increase the performance, ultimately to levels required for detecting Earthlike planets.

“Just imagine -- when you go outside and look at a star in the night sky, you might be looking at a planet just like the Earth, hidden in the star’s glare,” said Ruslan Belikov, the project lead for MSWC. “Also, chances are that the star you’re looking it is a multi-star system. I just can’t wait until we lift veils of starlight to unlock the secrets that lie on the planets within.”

Acknowledgment: This work was supported by NASA Internal Scientist Funding Model (ISFM) program and led by the NASA Ames Research Center. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).

PROJECT LEADS

Dr. Ruslan Belikov, NASA Ames Research Center (Principal Investigator) and Dr. Eduardo Bendek (Institutional PI), NASA Jet Propulsion Laboratory.

SPONSORING ORGANIZATION

NASA Astrophysics Division (Internal Scientist Funding Model/ Strategic Astrophysics Technology [SAT])

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Rare Antarctic meteorite is one of the largest ever found

Astronomy News - 25 January 2023 - 9:46am

Antarctica is the perfect place to go meteorite hunting, as space rocks stand out on the wide fields of ice, and researchers have found a new crop

Webb Unveils Dark Side of Pre-stellar Ice Chemistry

Astronomy News - 24 January 2023 - 9:50am
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JWST has seen building blocks of life in a dark, cold cloud in space

Astronomy News - 24 January 2023 - 9:49am

The James Webb Space Telescope has observed a frigid cloud of dust and gas where stars are forming, and it found frozen elements that are crucial for the development of life

Winchcombe meteorite: Is this the UK's most important fireball?

Astronomy News - 23 January 2023 - 9:43am

The meteorite crashed in England in 2021, containing water that was a near-perfect match for that on Earth.

Why the Hubble telescope is still in the game — even as JWST wows

Astronomy News - 23 January 2023 - 9:42am

Nature, Published online: 20 January 2023; doi:10.1038/d41586-023-00136-8

NASA’s nearly 33-year-old observatory still has plenty of top science to do, and astronomers want to extend its lifetime.

Hubble Captures Cosmic Treasure Trove

Astronomy News - 23 January 2023 - 9:41am
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Amazing JWST images show a nebula shaped by a multi-star smash-up

Astronomy News - 23 January 2023 - 9:41am

The stunning filaments and coils of light that make up the Southern Ring Nebula were shaped by as many as five stars all orbiting one another in a complex dance

Amazing JWST images show a nebula shaped by a multi-star system

Astronomy News - 23 January 2023 - 9:41am

The stunning filaments and coils of light that make up the Southern Ring Nebula were shaped by as many as five stars all orbiting one another in a complex dance

Light pollution: Huge fall in stars that can be seen with naked eye

Astronomy News - 20 January 2023 - 9:49am

Our view of the stars has been reduced every year over the last decade by artificial light pollution.

Night skies are brightening — and dimming the outlook for astronomy

Astronomy News - 20 January 2023 - 9:49am

Nature, Published online: 19 January 2023; doi:10.1038/d41586-023-00103-3

Fewer stars are visible worldwide now than a decade ago, according to measurements by community scientists.

Up to 74% of planets in the ‘habitable zone’ may not be good for life

Astronomy News - 20 January 2023 - 9:48am

Many planets that have the right temperatures for liquid water on their surfaces used to be too hot or too cold, which may affect their ability to host life now

Spin-down by dynamo action in simulated radiative stellar layers

Astronomy News - 20 January 2023 - 9:47am
Science, Volume 379, Issue 6629, Page 300-303, January 2023.

Stellar initial mass function varies with metallicity and time

Astronomy News - 19 January 2023 - 10:08am

Nature, Published online: 18 January 2023; doi:10.1038/s41586-022-05488-1

A direct star-counting method of about 93,000 M-dwarf stars in the solar neighbourhood indicates a variable stellar initial mass function that depends on both metallicity and stellar age.

The mass distribution of newborn stars depends on age and amount of metal

Astronomy News - 19 January 2023 - 10:07am

Nature, Published online: 18 January 2023; doi:10.1038/d41586-022-04517-3

The variation in the mass of newly born stars has been debated for decades. A star-count analysis now reveals that the initial mass of stars varies with their levels of metal elements, and that populations of stars born earlier in the Universe’s history contain fewer low-mass stars than do younger populations.

Dainty eater: black hole consumes a star bit by bit

Astronomy News - 19 January 2023 - 10:06am

Nature, Published online: 18 January 2023; doi:10.1038/d41586-023-00074-5

Repeating bursts of X-rays lead scientists to a black hole that eats in spurts.

Star graveyard revealed in super-clear image of the Milky Way

Astronomy News - 19 January 2023 - 10:06am

Nature, Published online: 19 January 2023; doi:10.1038/d41586-023-00110-4

Detailed radio observations turn up previously unseen remnants of dying stars in the Galaxy.