Sky & Telescope - USA (2019-09)

NEWS NOTES

12 SEPTEMBER 2019 • SKY & TELESCOPE

GALAXY

The Milky Way Used to Burst with Stars

NEW RESEARCH SHOWS that just a

couple billion years ago, our quiet gal-

axy 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

the European Space Agency’s Gaia satel-

lite, 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 bright-

ness and color information for 2.9 mil-

lion stars listed in Gaia’s second data

release (S&T: Aug. 2018, p. 9). Then

they fed this information into a simula-

tion, 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 sug-

gested that around this time the Milky

Way had swallowed a Small Magellanic

Cloud–size galaxy, dubbed Gaia-Encela-

dus. That merger might have stimulated

a rush of star formation before eventu-

ally quashing it — the star-formation

rate steadily declined for the next 5

billion years.

Then, our galaxy experienced a sec-

ond stellar baby boom, most likely due

to another collision with a gas-rich sat-

ellite 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 forma-

tion 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

p This plot shows how many Suns’ worth of

stars formed per year through the last 10 billion

years of our galaxy’s history.

p This representation shows Gaia’s measure-

ments of 1.7 billion stars in the Milky Way and

neighboring galaxies.

Years of age (billions of years)

Mathematical

fit to data

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IN BRIEF

NASA’s Artemis Gets

Budget Boost

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 FY

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 $

billion. NASA is already moving ahead with

some Artemis contracts, including $45.5 mil-

lion for 11 companies participating in the Next

Space Technologies for Exploration Partner-

ships. 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.

Exocomets Detected

Transiting Beta Pictoris

Astronomers have discovered three exocom-

ets transiting the nearby star Beta Pictoris.

At only 23 million years old, Beta Pic is in the

“young adult” phase of starhood, still sur-

rounded by a debris disk of dust and gas. Us-

ing the Transiting Exoplanet Survey Satellite

(TESS), Sebastian Zieba (University of Inns-

bruck, 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 coau-

thor 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, fl uffy, 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

Amateur Filmed Solar

Eclipse in 1900

On May 28, 1900, amateur astronomer and

fi lmmaker John Nevil Maskelyne captured the

fi rst-ever movie of a total solar eclipse from

the small town of Wadesboro, North Carolina.

Seven seconds into the reconstructed fi lm,

released by the Royal Astronomical Society

and British Film Institute, a tiny bead of sun-

light escapes through a lunar valley and cre-

ates a diamond ring shape around the Sun.

The rest of the movie shows a faintly oblate

solar corona that’s brighter near the equa-

tor 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 fi lm 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 fi lm at the British Film

Institute, and her colleagues restored and

digitized the fi lm.

■ MONICA BOBRA

View the fi lm at https://is.gd/oldeclipse. CH

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