Sky & Telescope - September 2019 - 12

NEWS NOTES
GALAXY

The Milky Way Used to Burst with Stars

p This plot shows how many Suns' worth of
stars formed per year through the last 10 billion
years of our galaxy's history.

the European Space Agency's Gaia satellite, along with sophisticated computer
algorithms, to delve into the Milky
Way's past. Their results appear in
April's Astronomy & Astrophysics.
First, the researchers selected brightness and color information for 2.9 million stars listed in Gaia's second data
release (S&T: Aug. 2018, p. 9). Then
they fed this information into a simulation, which reconstructed our galaxy's
star-formation history.
The results suggest that our galaxy
was churning out stars 10 billion years
ago. Other studies have already suggested that around this time the Milky
Way had swallowed a Small Magellanic
Cloud-size galaxy, dubbed Gaia-Enceladus. That merger might have stimulated
a rush of star formation before eventually quashing it - the star-formation
rate steadily declined for the next 5
billion years.

IN BRIEF
NASA's Artemis Gets
Budget Boost

Exocomets Detected
Transiting Beta Pictoris

Amateur Filmed Solar
Eclipse in 1900

Astronomers have discovered three exocomets transiting the nearby star Beta Pictoris.
At only 23 million years old, Beta Pic is in the
"young adult" phase of starhood, still surrounded by a debris disk of dust and gas. Using the Transiting Exoplanet Survey Satellite
(TESS), Sebastian Zieba (University of Innsbruck, Austria) and colleagues have tracked
the star's brightness over 105 days, revealing
three distinct dips that indicate the passage
of exocomets. The dips are asymmetric, not
periodic, and the longest one lasts about two
days. "What we are seeing is not the comet
nucleus itself, but the material blown off the
comet and trailing behind it," explains coauthor Konstanze Zwintz (also at the University
of Innsbruck). That material dims the star's
light. However, the dips in the light curve do
not distinguish between big, fluffy, close-in
exocomets and small, dense ones farther
from the star. To better characterize these
exocomets, the team suggests taking spectra
at the same time as future transits. The results
appeared in May's Astronomy & Astrophysics.
■ MONICA YOUNG

On May 28, 1900, amateur astronomer and
filmmaker John Nevil Maskelyne captured the
first-ever movie of a total solar eclipse from
the small town of Wadesboro, North Carolina.
Seven seconds into the reconstructed film,
released by the Royal Astronomical Society
and British Film Institute, a tiny bead of sunlight escapes through a lunar valley and creates a diamond ring shape around the Sun.
The rest of the movie shows a faintly oblate
solar corona that's brighter near the equator and dimmer near the poles. Maskelyne
compensated for the change in brightness
at totality by adjusting the exposure and
camera aperture for each image. After the
eclipse, Maskelyne brought his film back to
England. But it disappeared into the Royal
Astronomical Society's archives until librarian
and archivist Sian Prosser and her colleagues
discovered it a few years ago. Bryony Dixon,
the curator of silent film at the British Film
Institute, and her colleagues restored and
digitized the film.
■ MONICA BOBRA

Average star formation rate
(solar masses per year)

12
10
8
6
4
Mathematical
ﬁt to data

2
0
10

Years of age (billions of years)

The White House has requested an extra
$1.6 billion toward NASA's accelerated return
of astronauts to the Moon, a program dubbed
Artemis for the Greek lunar goddess. NASA
had already been planning to return to the
Moon by 2028, but the new initiative aims
to put boots on the lunar surface by 2024.
The additional funds put NASA's FY2020
budget request at $22.6 billion - about a 5%
increase over FY2019. The increase would
come from a surplus in the Pell Grant program
for low-income college students. However,
estimates of funds necessary to achieve a
2024 landing range from $25 billion to $40
billion. NASA is already moving ahead with
some Artemis contracts, including $45.5 million for 11 companies participating in the Next
Space Technologies for Exploration Partnerships. The companies' six-month contracts
will go toward the development of elements
involved in transferring to lunar orbit, landing
on the Moon's surface, and refueling.
■ DAVID DICKINSON

Find more details about the budget at
https://is.gd/ArtemisBudget.

S E P TE M B E R 2 019 * SK Y & TELESCOPE

p This representation shows Gaia's measurements of 1.7 billion stars in the Milky Way and
neighboring galaxies.

Then, our galaxy experienced a second stellar baby boom, most likely due
to another collision with a gas-rich satellite galaxy. This time, the proliferation
of new stars lasted some 4 billion years,
peaking about 2 billion years after it
started. The galaxy churned out enough
stars during this period to populate half
of its thin disk. The rate of star formation has been diminishing ever since,
down to today's rate of a Sun's worth of
stars per year.
If the Milky Way really did engulf a
companion galaxy a couple billion years
ago, one thing's for sure: Our night sky
wouldn't be the same without it.
■ MONICA YOUNG

View the ﬁlm at https://is.gd/oldeclipse.

CH A RT: ROG ER M OR E T A L. / ASTR ONOMY &
ASTR OPHYSICS 2019; G AIA: ESA / G AIA / DPAC

NEW RESEARCH SHOWS that just a
couple billion years ago, our quiet galaxy was birthing stars at a rate up to 10
times higher than it is today.
Roger Mor (University of Barcelona,
Spain) and colleagues used data from

https://www.is.gd/oldeclipse https://www.is.gd/ArtemisBudget

Sky & Telescope - September 2019

Table of Contents for the Digital Edition of Sky & Telescope - September 2019