2020-04-02_Science_Illustrated

14 | SCIENCE ILLUSTRATED

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BY THE WAY

The Milky Way has a new profile

Our galaxy is not flat as a pancake, as it is often

depicted. Astronomers have produced a new image

which shows that its profile is slightly S-shaped.

The image was created by measuring the light from

2400 special stars known as cepheids. They are very

bright and can be observed across the galaxy, and it

is particularly easy to calculate the distance to them.

Adopted galaxy keeps on giving

Spanish astronomers have found evidence

of a small galaxy which was swallowed by

the Milky Way about 10 billion years ago. By

determining the ages of almost 600,000 stars,

they identified those which our galaxy probably

‘adopted’ and those that were born from

the small galaxy’s gases since the adoption.

Black hole sends light signals

The black hole at the centre of our galaxy has

begun to shine much more brightly than

astronomers have observed over the past 20 years.

The light is produced by rotating gas that swirls

closely around the hole, but astronomers do not

know why it has become brighter. It might be that the

gases were disturbed by the gravity of a nearby star.

The biggest bar in the galaxy

The Milky Way is a barred spiral galaxy,

because in its interior it includes a bar-

shaped structure that consists mainly of old, red

stars. Astronomers have combined new data from

the Gaia telescope with earlier observations to

produce a 3D reconstruction of the bar. The aim is

to solve the mystery of how the bar was produced.

A new gel makes sperm cells with X chromosomes slower, so they can

be distinguished or separated from sperm cells with Y chromosomes.

BIOLOGY A new discovery can

make it easier to determine the

gender resulting from a

pregnancy. By studying mouse

sperm, Japanese scientists from

Hiroshima University have

identified previously unknown

differences between sperm cells

with an X chromosome and those

with a Y, finding 18 genes in the X

sperm cells that code for proteins

which protrude from the surface.

The genes are not active in sperm

cells with Y chromosomes.

The scientists subsequently

produced a gel with molecules

that bind to the proteins in

question, then made sperm cells

swim through it. The cells with X

chromosomes were delayed by

the molecules in the gel, but it did

not affect Y chromosome cells. So

a simple elimination race via the

gel can separate the sperm cells

in a way that, according to the

scientists, is cheap and gentle,

and has no risk of harming them.

The scientists do not intend

the method for humans seeking

either a boy or a girl, but it could

have useful applications in

animal breeding. Dairy cattle

breeders prefer female

calves for milking,

whereas beef farmers

would like male calves. Pig

breeders often prefer female

pigs, because it is necessary to

neuter male pigs in order that

their meat does not get an

unpleasant taste. The Japanese

scientists hope that the method

can lead to more humane

methods of animal breeding.

Sex selection by slowing down

sperm cells with the X factor

AND TALKING OF THE MILKY WAY ...

The Sun

Milky Way

Absorbed galaxy

Centre of the Milky Way

The MWay barilky

20,000 light years

Light from the centre

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SCIENCE UPDATE